The present invention relates to a sheet collecting device that collects and sets sheets carried out from an image forming apparatus or the like, into a bundle. In particular, the present invention relates to improvements in a collecting tray structure on which sheets are orderly aligned with one another before being transferred from a tray position, at which the sheets are set, to a processing position located away from the tray position.
Collecting devices of various structures have been commonly used to stack sheets sequentially carried out from an image forming apparatus, on a tray. A typical known collecting structure is a device comprising a tray inclined at a predetermined angle and on which sheets conveyed from above are stacked, the tray having a regulating wall at its end (leading end or trailing end) so that sheets fall down on the tray under their own weights and abut against the regulating wall for alignment.
Bookbinding devices and the like stack and set sheets into a bundle, align the sheets on the tray with one another at one end in their width direction and at another end (leading end or trailing end) in their longitudinal direction, and transfer the sheet bundle to a processing position different from the collecting position for pasting or stapling. These devices need to accurately align the sheets on the tray with one another. If the sheets edges are misaligned when the sheets are set on the tray, the bookbound sheets may have missing pages or not be aesthetically pleasing. Thus, bookbinding devices set the collecting tray in a substantially horizontal direction or at an inclination small enough to prevent the sheets from moving under their own weight. A preferred collecting tray structure includes one in which the sheets are reliably abutted against a regulating member for alignment using an aligning roller or another aligning means provided on the tray.
For example, Japanese Patent Laid-Open Publication No. 2003-103959 has roller means disposed above a horizontally located tray and abuts the uppermost one of sheets collected on the tray against a regulating member disposed at the trailing end of the sheets, with the side edge of the sheet moving along a guide plate. Thus, compared to the conventional technique for abutting sheets against the predetermined regulating member for alignment under their own weight, the technique in this document can forcibly move the sheet via conveying means such as a roller to abut it against the regulating member located at the leading end of the sheet, allowing the sheet edge to reliably abut against the regulating member for alignment regardless of the condition of the sheet.
When sheets are stacked and housed on the tray having the aligning means thereon for aligning the bundled sheets with one another at their edge, wherein the leading or trailing end of each sheet is abutted against the regulating means for alignment, as described above, the tray may disadvantageously be swung by vibration of the device, loosening the sheet bundle. For example, when the regulating means located at the leading or trailing end of the tray has a top surface regulating surface and is swung up and down every time sheets enter the tray, motion of the regulating means may vibrate the tray, loosening the sheet bundle on the tray.
This phenomenon will be described with reference to FIG. 8. A tray 100 has a regulating member 101 having an edge engaging surface 101a against which the edge, i.e., the trailing edge, of sheets is abutted for regulation and a pressure regulating surface 101b that corrects the upward warpage of the sheets. Then, vertical swing of the pressure regulating surface 101b may swing the tray 100 in the direction of an arrow in the figure owing to a structure for mounting the tray on an apparatus frame. Thus, when the tray is swung by vibration of the device, the sheets on the tray may be loosened as shown in FIG. 8(b).
The present invention is based upon knowledge that when a plate member with a small mass is disposed on a tray (main body) on which sheets are placed, so as to be movable in a regulating direction, it prevents possible swing of the tray main body in the regulating direction, caused by vibration of the device, from propagating to the sheets.
One object of the present invention is to provide a sheet feeding device that keeps sheets on a tray aligned with one another even when the tray undergoes device vibration or any other external impact when the edge of sheets is abutted against a regulating member for alignment.
Another object of the present invention is to provide a bookbinding device which sets sheets with images formed thereon on a collecting tray for alignment and then subjects the sheet bundle to bookbinding, the bookbinding device being capable of orderly aligning the sheets with one another at their edge.
The other objects and features of the present invention will be apparent from description of embodiments based on accompanying drawings.